The present invention relates to a method for treatment of the heavy fraction resulting from thermal cracking of high molecular-weight hydrocarbonaceous materials -- typically, plastics, and it relates particularly to a method capable of effectively separating and removing carbon and other non-evaporable materials contained in said heavy fraction.
As is generally known, in the case of thermal cracking of high molecular-weight hydrocarbonaceous materials like plastics by means of, for instance, a melter-type cracking still, a fluid-bed type cracking furnace or the like, there is produced a heavy fraction containing solid impurities such as carbon and relatively heavy liquid hydrocarbons. Especially in the case of thermal cracking of chlorine-containing plastics and thermosetting plastics, generation of carbon is remarkable. Hydrocarbons contained in the heavy fraction usually become light through the process of re-cracking, but such impurities as carbon and the like contained in the heavy fraction are gradually accumulated within the cracking system unless they are discharged to the outside thereof. According to the prior art, the carbon accumulated within the cracking system is drawn out of the system as occasion demands to be disposed of, but this method is defective in that it cannot sufficiently meet the current public demand for prevention of public nuisances as much as possible.
In the meantime, as a method of separating solids from liquids, the method of separating by filtration is most popular. However, in the case of the foregoing heavy fraction, not only said fraction per se is very viscous but also some of the carbon admixed therewith is in the form of fine particles, so that the conventional method of separating by filtration is ineffective in separating said carbon satisfactorily.
The present invention is intended to provide a method of treating the foregoing heavy fraction which renders it possible to separate said heavy fraction into hydrocarbons and such impurities as carbon and others, and it utilizes the properties of said heavy fraction that carbon and other impurities contained therein do not evaporate at a temperature permitting evaporation of hydrocarbons contained therein.